The present invention relates to the insulation of furnace walls and the insulated furnace wall produced by the method. It represents an improvement over known methods and most particularly over the method for reducing the thermal inertia of furnace or oven walls described in U.S. Pat. No. 4,194,036 issued Mar. 18, 1980. The present invention utilizes insulating modules in a new method to produce a new and improved insulated furnace wall.
In general, the present invention involves the insulation of furnace walls by applying a dual layer insulation. The first layer of insulation, which is to be applied to the furnace wall has much less rigorous requirements with respect to its resistance to thermal decomposition, as the second layer is applied thereover to reduce its exposure. The second layer of insulation is applied over the first layer of insulation and is exposed to the full furnace operating temperatures. It is for this layer that a unique insulating module of the type disclosed in U.S. Pat. No. 4,194,039 noted above, is to be used to give the resulting wall its unique insulating characteristics. In addition, as furnace insulation is generally applied in modular form, the second layer can be applied in an offset manner with respect to the seams of the first layer of insulation. This reduces leakage of both gases and heat through the insulating layer.
A two-layer heat insulating liner for furnace construction, wherein the second layer of insulation is generally disposed in non-alignment with the seams of the first layer of insulation, is disclosed in British Pat. No. 1,555,459, published Nov. 7, 1979. However, the insulating module used in the present invention is not described in this patent.
The insulation of ovens and furnaces using modules of refractory fibers disposed substantially end-on to the wall of the furnace, has been practiced for a long time. Thus, for example, U.S. Pat. No. 4,194,036 discloses a module and method of use, similar to that which is employed in the practice of the present invention. However, this patent is directed to only a single layer of modules.
Another type of module for use in insulating furnaces or ovens is disclosed in U.S. Pat. No. 3,930,916, issued Jan. 6, 1976. Shown is a composite module wherein the hot face is formed of insulating fibers secured end on to a layer of vermiculite block which, in turn, is bolted to a steel sheet for use in an oven. Individual modules are secured to the oven wall.
Other patents which describe various insulating modules for attachment to oven walls or the like include U.S. Pat. No. 3,819,468 to Sauder et al; U.S. Pat. No. 3,993,237 to Sauder et al.; and U.S. Pat. No. 3,940,244 to Sauder et al. These are related applications which U.S. Pat. No. 3,940,244 is particularly concerned with a dual layer module to be applied to a furnace wall.